科研之友
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摘要
In this study, two sediment core samples were collected from the tubeworms area (site ROV06) and mussel area (site HM101) of the Haima cold seep, northern South China Sea. We extracted the lipid biomarkers, analyzed the contents and stable carbon isotopic values to study the source of the organic matter in seabed surface sediments, the distribution of microbial communities and their response to the seep leakage intensity. Alarge amount of crocetane, PMI, archaeol and sn2-hydroxyarchaeol (sn2OH-Ar) related to anaerobic methanotrophic archaea (ANME) and iso-C15 and ai-C15 fatty acids produced by sulfate-reducing bacteria (SRB) were detected. The extremely negative δ13C values of these lipid biomarkers (as low as ?126%0 for archaea biomarkers and ?89 %0 for sulfate-reducing bacteria biomarkers) indicated that anaerobic oxidation methane (AOM) occurred in the sediments. Crocetane was detected in the sediments of both ROV06 and HM101 sites, and most of the ratio of sn2-OH-Ar/archaeol was higher than 1, while the ratio of ai-C15/ iso-C15fattyacid was lower than 2, indicating dominated community of ANME-2/DSS consortium in both site and a strong methane leakage intensity. The surface sediment of ROV06 site contained crocetane, whereas the low ratio of sn2-OH-Ar/archaeol(less than 1) and high ratio of ai-C15/iso-C15 fatty acid (>2.1) indicated a mixed communities of ANME-1 /DSS and ANME-2 /DSS and the methane leakage intensity from bottom to surface of ROV06 station with a decreasing trend. The δ13C values of methane (?58%0~? 53%0) were calculated based on the carbon isotopic fraction (Δ:?50%0) of ANME-2 and the mean δ13C values of the archaea biomarkers (PMI, archaeol, sn2-OH-Ar), indicating a mixture of thermogenic and biogenic source of methane. Methane at ROV06 and HM101 sites showed similar δ13C values, whereas the δ13C values of the biomarkers derived from SRB at ROV06 was lower than that at HM101 (Δδ13C:18%0), which may be related to the absorption of sulfide and the release of sulfates by sulfur-oxidizing bacteria, a symbiotic bacterium of the tubeworms. The continuous release of sulfates was likely to greatly enhance AOM progress, resulting in more 13C-depleted inorganic carbon in the sediment.
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